This invention relates to a medical device for treating a heart valve insufficiency, with an endoprosthesis which can be introduced into a patient's body with minimal invasion and automatically expanded in order to position and secure a heart valve prosthesis in the patient's aorta, which endoprosthesis has at least three positioning arches for automatically positioning the medical device in the patient's aorta and a retaining segment with retaining arches for accommodating a heart valve prosthesis, and the endoprosthesis assumes a first pre-definable mode during the process of introducing it into the patient's body and a second pre-definable mode in the state when the medical device is implanted, and when the medical device is in a collapsed state when the endoprosthesis is in the first mode and in an expanded state when the endoprosthesis is in the second mode.
The operating principle of such a device is known from medical technology. Biological or mechanical valve models are currently available as a means of replacing human heart valves, which are securely stitched in the heart valve base through an opening in the thorax during surgery once the diseased heart valve has been removed. In order to undertake this intervention, the patient's circulation must be supported by a heart and lung machine and the heart is arrested whilst the heart valve prosthesis is being implanted. This is a risky surgical intervention which places the patient at risk accordingly and which involves a long post-operative phase of treatment. In multi-morbid patients in particular, the risk of carrying out such intervention is no longer justifiable.
In more recent times, treatment methods which are minimally invasive have been developed, which are distinctive due to the fact that the intervention can be carried out with a local anaesthetic. This option is based on the use of a self-expanding stent with a collapsible heart valve prosthesis, which is implanted in the human body by means of an appropriate catheter system. A self-expanding heart valve prosthesis of this type can be fed by means of a catheter system through a main artery or vein to the implantation site at the heart. Once the implantation site is reached, the stent, which is made up of several self-expanding stent segments which can be angled relative to one another, is successively unfolded. Once unfolded, the heart valve prosthesis can be anchored in the respective blood vessel at least in the vicinity of the heart with the assistance of anchoring hooks for example. The actual heart valve prosthesis is then disposed directly in the proximal region of the stent or endoprosthesis.
Patent publication DE 100 10 074 A1, for example, discloses a device for securing and anchoring heart valve prostheses, which essentially comprises shaped wire elements connected to one another. In this instance, different arches are used as a means of reliably securing and anchoring the heart valve prosthesis. To this end, the device described in this specification has three identical pairs of arches respectively disposed at a distance of 120° apart. These arches are connected to one another by fixed body joints, and the fixed body joints assume the function of pivot bearings. Arches bent in the opposite direction are also provided, which form lever arms which are of identical length as far as possible, to enable a reliable seating of the arches, even in the event of peristaltic movements of the heart and blood vessel, and afford a reliable seal for an implanted and secured heart valve prosthesis.
With the known solution, however, there is still a risk of heart valves being incorrectly implanted. In particular, this is attributable to the fact that the heart valve prosthesis must be exactly positioned and longitudinally oriented. In particular, it requires enormous skill on the part of the surgeon performing the treatment—if it is possible at all—to position a stent which has a heart valve prosthesis at its proximal end and to do so accurately enough in the vicinity of the patient's diseased heart valve to ensure both correct lateral positioning accuracy and a correct longitudinal position of the heart valve prosthesis as far as possible.
Amongst other things, incorrect implantation of a heart valve prosthesis that is not optimally positioned can lead to inadequate sealing or valve insufficiency, which places considerable stress on the ventricle. If a heart valve prosthesis is implanted too far above the actual heart valve plane, for example, this can cause the outlets of the coronary vessels (coronaries) to close, thus leading to fatal coronary ischaemia due to heart infarction. This being the case, it is absolutely vital that both the lateral positioning accuracy and longitudinal positioning accuracy of a heart valve prosthesis meet requirements.
In the case of conventional implantation techniques whereby self-expandable heart valve prostheses are fed to the implantation site at the heart through a main artery of the patient requiring minimal invasion, for example, the prosthesis is usually introduced by means of a guide wire and with the aid of catheters, in which case it is standard practice to use a balloon catheter for this intervention. Although it is possible to monitor and control the introduction process during such an intervention, for example with the aid of an X-ray system (heart catheter laboratory=HCL) or with the aid of ultrasound (trans-oesophageal echocardiagram=TEE), the heart valve prosthesis is still of relatively large dimensions in spite of being collapsed whilst it is being introduced and it is often not possible to obtain the required positioning accuracy due to restricted ability to manoeuvre, and in particular to ensure correct longitudinal positioning of the heart valve prosthesis to be implanted with the fixing elements attached to it accordingly. Especially if there is a risk that the coronary vessels might close, implanting the heart valve prosthesis in a position angularly offset from the optimum implantation site represents a particular risk for the patient.
When designing a heart valve prosthesis, allowance must specifically be made for the considerable forces which act on the prosthesis, including during the filling phase of the heart cycle (diastole), and reliable anchoring is necessary in order to prevent the implanted heart valve prosthesis from becoming detached.
Accordingly, it must be possible to manoeuvre the heart valve prosthesis in the relevant access vessel as efficiently as possible during the implantation process in order to ensure optimum positioning accuracy on the one hand, and on the other hand, the implanted heart valve prosthesis must be firmly anchored at the implantation site in order effectively to prevent the prosthesis from shifting subsequently.
The underlying problem addressed by this invention is the fact that known devices used for the transvascular implantation of heart valve prostheses are often not suitable for implanting a heart valve prosthesis easily to the required degree of positioning accuracy. Furthermore, until now, it has only been possible to correct an incorrectly positioned heart valve prosthesis that has already been partially implanted with great difficulty—if at all.